1. Technical Field
The present invention relates to a display device.
2. Description of the Related Art
In recent years, demand has been increased for display devices for a mobile apparatus and the like such as a cellular telephone and electronic paper. In such display devices, one pixel includes a plurality of sub-pixels that output different colors. Such display devices allow one pixel to display various colors by switching ON/OFF the display of the sub-pixels. Display characteristics such as resolution and luminance have been improved year after year in such display devices. However, an aperture ratio is reduced as the resolution increases, so that luminance of a backlight needs to increase to achieve high luminance, which leads to increase in power consumption of the backlight. To solve this problem, techniques have been developed for adding a white pixel serving as a fourth sub-pixel to red, green, and blue sub-pixels known in the art (for example, refer to Japanese Patent Application Laid-open Publication No. 2012-108518). According to these techniques, the white pixel enhances the luminance to lower a current value of the backlight and reduce the power consumption.
In a case in which the current value of the backlight is not lowered, the luminance enhanced by the white pixel can be utilized to improve visibility under outdoor external light (for example, refer to Japanese Patent Application Laid-open Publication No. 2012-22217 (JP-A-2012-22217)). According to the technique of JP-A-2012-22217, an expansion coefficient for expanding an input signal is varied according to brightness of the input signal. Accordingly, the expansion coefficient increases as the brightness decreases, that is, as the gradation level decreases, and the expansion coefficient decreases as the brightness increases, that is, as the gradation level increases. As a result, the luminance on the low gradation side increases, and the visibility of the display device in the outdoors is improved.
The display device is desired to be lower in power consumption, or desired to be improved in visibility in the outdoors.
For the foregoing reasons, there is a need for a display device whose power consumption is suppressed or whose visibility in outdoors is improved.